I picked up a used Boss TU-60 "digital strobe" tuner identical to this one:
In short, you select the string you want to tune and the LEDs will strobe either left or right depending on the pitch of the input; when in tune with the selected note the LEDs will stop moving.
The tuner seemed to work when the rotary knob was set to the high E (1E) setting. However, in the other positions only a single, seemingly random LED would stay lit. If I wiggled/fiddled with the knob it would sometime work very briefly for a couple of seconds. Based on that I figured the rotary switch was the problem.
I took the unit apart, and checked all of the solder joints (it's a single PCB) including those around the rotary switch. Nothing looked flaky. The switch is sealed, so I'm not sure if getting something like Deoxit inside to clean the internal contacts is an option. The only other options I can think of are reflowing the switch contacts on the PCB or just replacing the switch.
I wasn't able to find a full service manual (or even a user manual) for the TU-60 online, but I did manage to find some pics of the front page which lists a part number for the rotary switch (SRN1016S-K15). I went dumpster diving on Google to see if I could source one and got absolutely zero hits.
Any suggestions or additional recommendations for troubleshooting or sourcing a replacement switch?
In short, you select the string you want to tune and the LEDs will strobe either left or right depending on the pitch of the input; when in tune with the selected note the LEDs will stop moving.
The tuner seemed to work when the rotary knob was set to the high E (1E) setting. However, in the other positions only a single, seemingly random LED would stay lit. If I wiggled/fiddled with the knob it would sometime work very briefly for a couple of seconds. Based on that I figured the rotary switch was the problem.
I took the unit apart, and checked all of the solder joints (it's a single PCB) including those around the rotary switch. Nothing looked flaky. The switch is sealed, so I'm not sure if getting something like Deoxit inside to clean the internal contacts is an option. The only other options I can think of are reflowing the switch contacts on the PCB or just replacing the switch.
I wasn't able to find a full service manual (or even a user manual) for the TU-60 online, but I did manage to find some pics of the front page which lists a part number for the rotary switch (SRN1016S-K15). I went dumpster diving on Google to see if I could source one and got absolutely zero hits.
Any suggestions or additional recommendations for troubleshooting or sourcing a replacement switch?
Manual for $15
However the whole thing can be bought in working order for $40-$60. (Some listings say "Rare!". In fact a lot of listings say that, which make us wonder...)
It's a good machine. I threw a lot away when found in school practice rooms at the end of the semester.
Clean the switch with Deoxit D5 and it will be fine.
Unlikely the switch is actually sealed, look for a small opening.
Unlikely the switch is actually sealed, look for a small opening.
Quick update: I re-flowed the solder joints around the switch. They didn't look bad before, and they look really good now. However, when testing it afterward outside of the plastic case I noticed that any pressure or flexing of the board would change the pattern and flashing of the LEDs. It could still be a switch issue, but now I suspect there's either an intermittent short at a solder joint or along a trace, or one of the logic components is starting to fail. I'll try the Deoxit drip down the shaft to see if that helps, but I'm not optimistic at this point.
I know that capacitors can go bad over time, but the only things I know to look for bulges or leaks. I looked for that when I was first inspecting the board but didn't see anything weird. Is there a way to confirm they're bad or on their way out short of removing them from the board and/or replacing them?
Dead capacitors are sometime but not always discernable by visual inspection. Specially the small and thin caps dry out over time. Either you measure them - or you replace them all. Measuring can by done normally in-circuit some minutes after power down. There are cheap Trańsistor/capacitance/ESR testers based on AVR Atmega328 available at AliBaba that will do this job.
I've ordered a budget (~$25) ESR meter from Amazon. Although not terribly precise, it is supposedly sufficient to gauge "good" versus "bad."
Still think an oxidized/dirty switch is the most likely thing. There are several pots that could be dirty too.
But since the electrolytic capacitors must be removed for testing, you might as well just replace them all.
Don't change the film or ceramics.
But since the electrolytic capacitors must be removed for testing, you might as well just replace them all.
Don't change the film or ceramics.
Its quite possible there is a bad solder joint or broken component leg. Try to localize the problem by applying pressure on solder joints, components with a pencil. Often solder joints can look good without an inspection scope to see full detail.
Good luck.
Good luck.
Did the same just some days ago to replace my broken LCR meter. It works surprisingly well!
I ordered the ESR meter to avoid having to do just that (remove them just for testing).
There seem to be several very cheap trim pots. Those are often a problem in older equipment,
but their setting methods are likely difficult to find out.
but their setting methods are likely difficult to find out.
There is no external access to those, so I would assume they're set at the factory and never adjusted afterward.
I took a second, closer look at the rotary switch, and it is all but airtight - no gaps at all in the assembly. The inner shaft with the split end for the knob has a flange that overlaps the outer threaded shaft. Any Deoxit sprayed on the inner shaft would run down to the flange and drip off its edge. I thought about trying to use a syringe to inject it, but I can't find a seam large enough to shoot it in through.
You won't be able to keep the cleaner from running around a bit, but it is necessary to use.
Place a paper towel with a hole in it over the switch shaft before spraying very gently down
the slight gap around the shaft. Rotate the switch shaft a few times, and then spray and rotate again.
The open frame trim pots are notorious for getting dirt and corrosion.
Place a paper towel with a hole in it over the switch shaft before spraying very gently down
the slight gap around the shaft. Rotate the switch shaft a few times, and then spray and rotate again.
The open frame trim pots are notorious for getting dirt and corrosion.